A conventional CMP machine includes a rotating polishing pad, a wafer carrier that is coupled and a conditioning disk. During CMP processing, liquid slurry of abrasive particles in a fluid is poured onto the rotating polishing pad and a semiconductor wafer is placed in the wafer carrier. The wafer carrier presses the wafer against the slurry and the rotating polishing pad while the carrier arm moves the wafer across the width of the polishing pad. The chemical reaction with the slurry and the physical erosion due to the contact with the abrasive particles causes material to be removed from the wafer and evens out any irregular topography, making the exposed wafer surface planar. The conditioning disk generally includes a diamond abrasive surface that is moved and rotated against the polishing pad. The conditioning disk keeps the particles removed from the wafer from accumulating on the polishing surface and maintaining the uniform abrasive character of the polishing pad.
As wafers are processed, the polishing pad is also worn down and eventually must be replaced. A problem with the CMP process is that the polishing surface of the pad can become uneven during wafer processing. An uneven polishing surface cannot polish a wafer properly and may result in uneven or defective wafer processing. Accordingly, what is needed is a CMP system control system that monitors the uniformity of the polishing surface and prevents uneven wear of the CMP polishing pad.